Surface transformation of silicon-doped hydroxyapatite immersed in culture medium under dynamic and static conditions.

A comparative study of in vitro bioactivity of hydroxyapatite (HA) and silicon-doped hydroxyapatite (SiHA) has been carried out by immersion in a cell culture medium with or without fetal bovine serum during 14 days in static and dynamic conditions. A specific bioreactor was developed for the experiments in dynamic conditions. Ceramic surface transformations were characterized by electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy before and after immersion. The monitoring of calcium, phosphate and proteins in immersion medium was also done during the experiment. The two hydroxyapatite surfaces immersed in cell culture medium under dynamic conditions were found to be more probably covered by a new Mg-enriched Ca-deficient apatite layer than surfaces immersed under static conditions. These results suggest that dynamic procedure and medium with serum macromolecules seem to be more adequate to predict the in vivo activity of bioceramics. Moreover, SiHA presented a higher capacity of protein adsorption.